Acoustic device



Dec. 24, 1935. B. B. GRACE ET AL ACOUSTIC DEVICE Filed March 21, 1954 .5. GRA c5 J. 51R R085? TON BY IN ME N TOPS WM a 1% A T TORNE V Patented Dec. 24, 1935 UNITED STATES ACOUSTIC DEVICE Bertram and James S. P. Rb.erton, Aid'wyclr, London, England, assignors to West; e'rn Electric Company, Incorporated, N ew York,

N. Y., a corporation of New York Application Marten, 1924, serial, its. 716,596 In Great Britain June 17, 1933 Claims. (01; 179 114) This invention relates to telephone or like receivers, and to headbands therefor, and more particularly though not exclusively, to so-called earphones, comprising a headband carrying two receivers, which are used to a considerable extent for wireless reception.

One object of the invention is to produce re ceivers which are simple in construction, and very cheap to produce and assemble, while being eiiicient and reliable in operation.

' A subsidiary object of the invention is to produce adjustable headbands which are made of the smallest possible number of parts, each of a form cheap to produce, and which are of pleasing appearance and comfortable to: wear.

The main feature of the invention comprises an assembly for use in a telephone receiver comprising an L-shaped magnetic member part or all of which is permanently magnetized, on one limb of which is mounted a complete or incomplete ring of magnetic material parallel or substantially parallel to the second limb the end of which carries a pole-piece which is parallel or substantially parallel to the first limb and is positioned substantially centrally with respect to the ring. These parts may be welded together and the whole receiver may be made and assembled without the use of screws or the like. By the term ring we mean to include closed or incomplete members of circular, oval, polygonal, or like shape, since such forms could be used, but we prefer to use a closed circular ring.

The invention will be fully understood from the following description of one embodiment of the invention with reference to the accompanying drawing, in which:

Fig. 1 shows a side view of a headband and receiver;

Fig. 2 shows a receiver with the casing in crosssection;

Fig. 3 shows a connecting terminal for use in the receiver;

Fig. 3A shows a cross-section of the connecting terminal shown in Fig. 3 along the line 3A-3A thereof;

Fig. 4 shows a plan view of the receiver along the line 44 of Fig. 2; and

Fig. 5 shows a cross-section of the receiver of Fig. 1 along the line 55 thereof, with the receiver cap omitted.

The receiver of the permanent magnet type is so constructed that no screws, nuts or the like are used in manufacture or assembly, while the coil is mounted directly on the pole-piece without spool checks.

The receiver comprises a casing I bored to receive the ends 2 of the spring clips 3 of the headbaiidt The receiverhas a permanent magnetsyStem comprising an L-shapedpermanent magnet fi to 5 the long armof which is Welded a pole-piece} formed of a nickel and iron alloy, as described in British Specification 295,668. 7, The pole-piece is recessed for about one-third of its length from the tip. It would be possible to form part only Oil the member t as a permanent magnet; p

To the short arm of the magnet is welded a tongue IT on a ring 5 of magnetic material which is c nc t with t aws-p ece- Tear n .6 is slightly spaced from the end of the member 4 so as to allow the ring to be bent slightly onthe tongue I! with respect to the pole-piece. The top of the pole-piece is adjusted so as to be flush with the top surface of the ring to within i002 inches. From the point of view of the magnetic field the ring need only extend about forty-five degree-s on either side of the connection to the magnet 4, but in order that it may be properly held in position it is better to have a complete ring. A terminal strip 1 of insulating material fits over the pole-piece 5 and is stuck to the magnet face. The ends of two coiled springs 8 are passed through holes in the strip 1, and are then twisted together to hold the springs in place. The cord passes through a hole 9 in the receiver casing and the end of each conductor is passed through the center of one of the coiled springs 8, and then between two of the coils which hold the end in place and give an electrical connection. The conductor ends could be passed into the springs, part of which could be flattened with pliers to grip the conductors. The coil turn nearest the pole-piece is separated somewhat from the main portion of the spring so that the terminals of the receiver coil l0 mounted on the pole- 40 piece 5 can be soldered thereto.

Alternatively the terminals 8 may be of the construction shown in Fig. 3, formed from two looped pieces of wire l8, IS, the two loops being arranged to hold the wires by spring tension, and being fixed to the strip 1 by an eyelet 20.

The receiver coil Ill is of simple construction being wound on thin ebonite cylinders without spool cheeks. The coil It is placed straight on to the pole-piece 5 of the receiver without spool cheeks and the end is stuck to terminal strip 1 which insulates it from the magnet 4.

The assembly consisting of the members 4, 5, 6,

I, 8, I0, is placed within the receiver casing, the outer edge of the ring 6 resting on the lip of the casing. The assembly is positioned by a pip, projection or lug II on the ring 6 engaging a V recess'in the lip of the casing so that the cord knot takes the strain on the cord. A paper ring of the same outside diameter as the ring 6 but of about one-third the Width is placed on the ring 6, and a plane metal diaphragm is placed over the paper ring. The whole assembly is held in place in the casing by an earpiece screwed thereto in well-known manner. The paper ring spaces the diaphragm from the ring 6 and allows it to vibrate more freely than if it rested directly on the wide ring 6.

The magnet is magnetized so that the center pole will repel the north-seeking pole of a compass needle. The magnetic flux passes through the pole-piece 5, radiates from the center to the periphery of the diaphragm, and passes via ring 6 back to the magnet. V

The headband consists of spring receiver casing holders 3. The straight legs of each holder pass through holes in the flanges of a member I3 of shallow channel cross-section. The legs l2 tend to spring apart (or together) and so frictionally hold the member I3 in any adjusted position. The headband comprises two wires M, the ends of which pass through further holes in the upper flange of the member l3, and are held in place by a rivet or eyelet l5 passing through the member I 3 The wires 14 are covered with artificial leather I6. Instead of the two Wires l4, and the mem ber I3, a single piece of strip-metal about one inch in width can be shaped as a headband, the ends being made of shallow crosssection, with the flanges drilled to take the legs I 2 of the holders 3.

What is claimed is:

1. An acoustic device comprising a unitary assembly comprising an L-shaped member of magnetic material, and a ring member of magnetic material mounted on one limb of said L-shaped member and substantially parallel to the other limb thereof, said ring member having a depending tongue portion for securing it to said L-shaped member.

2. An acoustic device comprising a unitary assembly comprising an L-shaped member of magnetic material, and a planar, ring member having a tongue at right angles to its plane, said ring member being fixed to one limb of said L-shaped member solely by said tongue with a slight clearance between the ring member and said limb.

3. An acoustic device comprising a unitary assembly comprising an L-shaped member of magnetic material, and a ring member of magnetic material having 2. depending tongue portion secured to one limb of said L-shaped member with a slight clearance between the ring member and the limb.

4. A telephone receiver comprising a casing having an open end containing a recess, and a unitary assembly in said casing and comprising a ring member supported on the casing open end and having a downwardly extending lug for en gagement with said recess, and a permanent magnet secured to and depending from the ring member opposite said lug.

5. A telephone receiver comprising a casing having an open end, a ring member supported on said open end and having a depending tongue portion, and a magnet structure secured to and dependent from said tongue portion.

BER'I'RAM B. GRACE. JAMES S. P. ROBER'I'ON. 

